1. Field of the Invention
This invention relates to a common mode choke coil used for removing noise signals which are equal in phase which are transmitted from the power line, and more particularly to a chip type common mode choke coil which is small in size and can be mounted on the surface of a printed circuit board, and its manufacturing method.
2. Discussion of the Related Art
Recently, as electronic circuits are decreased in size, increased in the degree of integration, and increased in the frequency handled, there has been a strong demand for provision of a chip type common mode choke coil which is small in size and can be mounted on the surface of a printed circuit board.
An example of a conventional common mode choke coil is a wound common mode choke coil (not shown), which is formed by winding two conductors on a ring-shaped magnetic core or bar-shaped magnetic core the same number of turns in the same direction.
The conventional wound common mode chock coil is disadvantageous in the following points. Since it is formed by winding the conductors on the magnetic core as was described above, the manufacturing method is intricate, and therefore the choke oil is not suitable for mass production, and accordingly it is high in manufacturing cost. In the case where the magnetic core is increased in size to some extent, in order to hold it and to connect the windings and to mount the choke coil on the surface of a printed circuit board, it is necessary to provide a housing seat with electrodes. Hence, it is difficult to miniaturize the wound common mode choke coil sufficiently, and it is not suitable to mount it on an electrical circuit including a number of circuit elements.